Automatic feedback mechanism and a medicament delivery device with user feedback capability

ABSTRACT

An automatic feedback mechanism for a medicament delivery device that notifies a user of a start of expulsion of medicament from a medicament container is presented where a plunger rod, a tubular extension member arranged to receive the plunger rod in the radial space, and wherein the tubular extension member has flexible tongues configured to releasably lock the plunger rod in a pre-tensioned state. The tubular operation member is arranged to receive the tubular extension member, where the tubular operation member in a first position is arranged to press the flexible tongues radially inwards to lock the plunger rod in the pre-tensioned state. A first resilient member is arranged inside the plunger rod to exert a force in the proximal direction. A signal generating member is arranged to partially surround the plunger rod such that movement of the signal generating member distally hits the inner distal surface generating an audible signal.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application a continuation of U.S. patent application Ser.No. 16/076,264, filed Aug. 7, 2018, which is a U.S. National PhaseApplication pursuant to 35 U.S.C. § 371 of International Application No.PCT/EP2017/051039 filed Jan. 19, 2017, which claims priority to EuropeanPatent Application No. 16155880.4 filed Feb. 16, 2016. The entiredisclosure contents of these applications are herewith incorporated byreference into the present application.

TECHNICAL FIELD

The present disclosure generally relates to medical devices. Inparticular, it relates to an automatic feedback mechanism for amedicament delivery device and to a medicament delivery devicecomprising such an automatic feedback mechanism, which thereby providesuser feedback.

BACKGROUND

When handling a medicament delivery device, it may be beneficial toprovide visual and/or tactile indication to a user regarding the currentstate of the medicament delivery device. For example, it is typicallyrequired that an automated medicament delivery device is maintained inposition at the injection site until the expelled dose has been properlyabsorbed and the liquid pressure created by the injected dose hassubsided in the injection site area. To this end, for automatedmedicament delivery devices it may be advantageous for a user to knowwhen the dose expulsion commences, facilitating determination of whenthe medicament delivery device may be removed from the injection site.

US2016/0008542 discloses an auto-injector for dispensing a liquidproduct with the intention to generate an acoustic and/or tactilesignal. The device includes a housing, a container, a blocking sleeve, adrive member, a spring, a needle protection sleeve, and a holdingelement supporting the spring. In the initial state, the holding elementis engaged with the drive member, which holding element is furthermaintained in position by the inner circumference of the blockingsleeve. To administer the product from the container the needleprotection sleeve is moved by an activation stroke. The holding elementis thereby disengaged from the drive member, and is instead set intoengagement with the blocking sleeve. The drive member is therebyreleased. The holding element can hence be moved some distance relativeto the housing, whereby the holding element transports the blockingsleeve. This causes the blocking sleeve to strike against a start signalstop formed by a mechanical holder. An acoustic and/or tactile signal isthereby emitted and signals the user of the device that dispensing ofthe product has started.

The disclosure of US2016/0008542 provides a solution for a specificconfiguration or design of an auto-injector. Moreover, the acousticand/or tactile signal is not really provided at the time when liquidexpulsion commences.

SUMMARY

A general object of the present disclosure is to provide an automaticfeedback mechanism for a medicament delivery device, and a medicamentdelivery device comprising such an automatic feedback mechanism, whichsolve or at least mitigate the problems of the prior art.

There is hence according to a first aspect of the present disclosureprovided an automatic feedback mechanism for a medicament deliverydevice, which notifies a user of a start of expulsion of medicament froma medicament container, wherein the automatic feedback mechanismcomprises: a plunger rod, a tubular extension member having a radialspace defined by an inner perimeter and an inner distal surface, whereinthe tubular extension member is arranged to receive the plunger rod inthe radial space, and wherein the tubular extension member has flexibletongues configured to releasably lock the plunger rod in a pre-tensionedstate, a tubular operation member arranged to receive the tubularextension member, which tubular operation member is movable relative tothe tubular extension member, wherein the tubular operation member in afirst position is arranged to press the flexible tongues radiallyinwards to lock the plunger rod in the pre-tensioned state, a firstresilient member arranged to be received inside the plunger rod to exerta force in the proximal direction, and a signal generating memberarranged to partially surround the plunger rod and having a distaltransversal end portion which in a first position is at a distance Dfrom the inner distal surface of the tubular extension member when theplunger rod is in the pre-tensioned state, wherein in an assembledstate, movement of the tubular operation member causes the flexibletongues to expand radially releasing the plunger rod to travelproximally and allowing the first resilient member to move the signalgenerating member distally the distance D such that the distaltransversal end portion hits the inner distal surface generating anaudible signal.

A audible indication of medicament expulsion may thereby be provided toa user.

The tubular operation member may according to one variation be rotatablerelative to the tubular extension member, wherein the tubular operationmember in a first rotational position is arranged to press the flexibletongues radially inwards to lock the plunger rod in the pre-tensionedstate. Thus, in an assembled state movement by rotation of the tubularoperation member causes the flexible tongues to expand radiallyreleasing the plunger rod.

According to one embodiment the signal generating member comprises anelongated U-shaped bracket having two longitudinally extending flexiblelegs provided with angled radial feet extending radially outward tosecure the signal generating member in the first position.

According to one embodiment the radial feet in the first position have aradial extension that exceeds the transverse dimension of the radialspace of the tubular extension member and where the radial feet in asecond position have a radial extension that is less than the transversedimension of the radial space of the tubular extension member.

According to one embodiment the radial feet in the first position have aradial extension that exceeds the radial extension of the radial feetwhen in the second position.

According to one embodiment the plunger rod has an external surfacewhich has a first section provided with a first guide structure arrangedto support and flex the signal generating member radially outwards, andto guide axial displacement of the signal generating member.

According to one embodiment in the initial position of the plunger rodthe axial overlap between the first section and the signal generatingmember corresponds to the distance of axial displacement of the plungerrod necessary for commencement of medicament expulsion.

According to one embodiment the signal generating member has legsarranged to interact with the first guide structure.

According to one embodiment first guide structure comprises axialgrooves in which the signal generating member is arranged to slide.

According to one embodiment the plunger rod has a second sectionarranged distally from and contiguous to the first section, which secondsection is defined by a longitudinal axially extending radial openingaxially aligned with the first guide structure, allowing radial inwardsflexing of the signal generating member towards its radially unbiasedstate.

According to one embodiment the second section extends to the distal endof the plunger rod.

According to one embodiment the plunger rod has a third section arrangeddistally from and contiguous to the second section, which third sectionis defined by a second guide structure axially aligned with thelongitudinal axially extending radial opening, and arranged to supportand flex the signal generating member radially outwards.

According to one embodiment the tubular extension member has firstengagement means for engaging with the signal generating member in theinitial position of the plunger rod, and wherein the tubular extensionmember has radial openings arranged distally from and aligned with thefirst engagement means, for allowing the signal generating member toflex radially outwards.

According to one embodiment the first section extends to the distal endof the plunger rod.

According to a second aspect of the present disclosure there is provideda medicament deliver device comprising a feedback mechanism according tothe first aspect.

One embodiment comprises a linearly displaceable medicament deliverymember cover configured to interact with the tubular operation member.

According to another aspect there is provided a medicament deliverydevice comprising a housing having a proximal end and a distal end, aplunger rod received by the housing and axially displaceable from aninitial position to a final position relative to the housing, a tubularextension member received by the housing and arranged to receive theplunger rod, which tubular extension member has a distal inner surface,a U-bracket received by the tubular extension member, wherein theplunger rod is arranged to be received by the U-bracket, and a firstenergy accumulation member arranged to bias the plunger rod in aproximal direction towards the proximal end and to bias the U-bracket ina distal direction which is opposite to the proximal direction, whereinin the initial position the plunger rod is arranged to flex theU-bracket radially outward towards the tubular extension member therebyengaging the U-bracket with the tubular extension member, whereby theU-bracket is distanced from the distal inner surface of the tubularextension member, and wherein the plunger rod and the U-bracket arearranged to allow the U-bracket to flex radially inwards towards aradially unbiased state of the U-bracket to disengage from the tubularextension member upon an axial displacement of the plunger rodcorresponding to a distance necessary for commencement of medicamentexpulsion, thereby providing axial displacement of the biased U-bracketto the distal inner surface of the tubular extension member.

Since the U-bracket is released from the tubular extension member whenthe plunger rod has been displaced a distance corresponding to thedistance necessary for commencement of medicament expulsion, the biasedU-bracket will rapidly be thrown in the distal direction and collidewith the distal inner surface of the tubular extension member whenmedicament expulsion has just commenced. In other words, the audibleand/or tactile feedback provided by this collision will occuressentially when medicament expulsion has just commenced. A user of themedicament delivery device will thereby be provided with a ratherprecise indication of the commencement of dose expulsion.

According to one embodiment the U-bracket has two radial arms, whereinthe radial feet are arranged to engage with the tubular extension memberin the initial position of the plunger rod.

According to one embodiment the plunger rod has a distal end opening,wherein the first energy accumulation member is arranged in and extendsfrom the distal end opening.

According to one embodiment U-bracket has a distal transverse endportion, and wherein the distal end of the first energy accumulationmember bears against the distal transverse end portion, thereby biasingthe U-bracket in the distal direction.

According to one embodiment the plunger rod has an external surfacewhich has a first section provided with a first guide structure arrangedto support and flex the U-bracket radially outwards, and to guide axialdisplacement of the U-bracket.

According to one embodiment in the initial position of the plunger rodthe axial overlap between the first section and the U-bracketcorresponds to the distance of axial displacement of the plunger rodnecessary for commencement of medicament expulsion.

According to one embodiment the U-bracket has legs arranged to interactwith the first guide structure.

According to one embodiment the first guide structure comprises axialgrooves in which the U-bracket is arranged to slide.

According to one embodiment the plunger rod has a second sectionarranged distally from and contiguous to the first section, which secondsection is defined by a longitudinal axially extending radial openingaligned with the first guide structure, allowing radial inwards flexingof the U-bracket towards its radially unbiased state.

According to one embodiment the second section extends to the distal endof the plunger rod.

According to one embodiment the tubular extension member has firstengagement means for engaging with the U-bracket in the initial positionof the plunger rod, and wherein the tubular extension member has radialopenings arranged distally from the first engagement means, for allowingthe U-bracket to flex radially outwards.

According to one embodiment the tubular extension member has firstengagement means for engaging with the U-bracket in the initial positionof the plunger rod, and wherein the tubular extension member has radialopenings arranged distally from and aligned with the first engagementmeans, for engaging with the U-bracket following radial outwards flexingof the U-bracket by the third section of the plunger rod.

According to one embodiment the first section extends to the distal endof the plunger rod.

One embodiment comprises a tubular rotator and a linearly displaceablemedicament delivery member cover, wherein the tubular rotator isrotatable, by linear displacement of the medicament delivery membercover, between a first rotational position in which the tubular rotatoris arranged to prevent the plunger rod from axial displacement from itsinitial position, and a second rotational position, wherein the tubularrotator and the tubular extension member are arranged to interact suchthat rotation of the tubular rotator towards the second rotationalposition releases the plunger rod to allow axial displacement of theplunger rod.

Generally, all terms used in the claims are to be interpreted accordingto their ordinary meaning in the technical field, unless explicitlydefined otherwise herein. All references to “a/an/the element,apparatus, component, means, etc. are to be interpreted openly asreferring to at least one instance of the element, apparatus, component,means, etc., unless explicitly stated otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

The specific embodiments of the inventive concept will now be described,by way of example, with reference to the accompanying drawings, inwhich:

FIG. 1 shows a perspective view of an example of a medicament deliverydevice;

FIG. 2 is an exploded view of the medicament delivery device in FIG. 1 ;

FIG. 3 a is a perspective view of one example of a rotator;

FIG. 3 b is a perspective view of one example of a tubular extensionmember and plunger rod;

FIGS. 4 a and 4 b are perspective views of an example of a plunger rodand a U-bracket;

FIGS. 5 a, 5 b, and 5 c show longitudinal sections of a portion of themedicament delivery device in FIG. 2 in a state prior to use, duringuse, and after use, respectively;

FIG. 6 is a perspective view of another example of a tubular extensionmember and plunger rod;

FIGS. 7 a and 7 b are perspective views of the plunger rod and aU-bracket of the example in FIG. 6 ;

FIG. 8 is a perspective view of yet another example of a plunger rod anda U-bracket; and

FIGS. 9 a and 9 b show longitudinal section of a portion of a medicamentdelivery device comprising the plunger rod and U-bracket in FIG. 8 in astate prior to use and during use, respectively.

DETAILED DESCRIPTION

The inventive concept will now be described more fully hereinafter withreference to the accompanying drawings, in which exemplifyingembodiments are shown. The inventive concept may, however, be embodiedin many different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided byway of example so that this disclosure will be thorough and complete,and will fully convey the scope of the inventive concept to thoseskilled in the art. Like numbers refer to like elements throughout thedescription.

The medicament delivery device disclosed herein may for example adisposable single-use medicament delivery device, such as anauto-injector, an inhaler or an eye dispenser. The medicament deliverydevice may be a regular medicament delivery device for medicamentadministration, or a trainer device.

The term “proximal end” as used herein refers to that end of amedicament delivery device at which medical expulsion can be provided.This is hence that end of the medicament delivery device that is to bepointed towards the injection or expulsion site. This definition alsoextends to any internal or external component of the medicament deliverydevice, i.e. the proximal end of any component is that which is closestto the proximal end of the medicament delivery device. The “distal end”is the opposite end relative to the proximal end. With “proximaldirection” is meant a direction from the distal end towards the proximalend, along the central axis of the medicament delivery device. With“distal direction” is meant the opposite direction to “proximaldirection”.

This disclosure concerns an automatic feedback mechanism for amedicament delivery device, and to a medicament delivery device withuser feedback capabilities.

The medicament delivery device has a housing having a proximal end and adistal end, a plunger rod received by the housing and axiallydisplaceable from an initial position to a final position relative tothe housing, a tubular extension member received by the housing andarranged to receive the plunger rod, which tubular extension member hasa distal inner surface, a signal generating member received by thetubular extension member, wherein the plunger rod is arranged to bereceived by the signal generating member, and a first energyaccumulation member arranged to bias the plunger rod in a proximaldirection towards the proximal end and to bias the signal generatingmember in a distal direction which is opposite to the proximaldirection.

In the initial position the plunger rod, which in the initial positionis in a pre-tensioned state, is arranged to flex or press the signalgenerating member radially outward towards the tubular extension memberthereby engaging the signal generating member with the tubular extensionmember. To this end, the plunger rod has a first section with a firstthickness or dimension, which presses the signal generating member whichin the initial position is mounted around the plunger rod, radiallyoutwards. The signal generating member is thereby engaged with thetubular extension member, retaining the distally biased signalgenerating member in a fixed axial position relative to the housing. Inthis axial position, the signal generating member is distanced from thedistal inner surface of the tubular extension member.

Prior to use, the plunger rod is arranged axially fixed in the initialposition. When the medicament delivery device is activated, i.e. when auser initiates medicament delivery, the plunger rod is released from theinitial position and is pressed in the proximal direction by the energyaccumulation member. When the plunger rod has been displaced a distancecorresponding to a distance necessary for commencement of medicamentexpulsion, the contact between the first section of the plunger rod andthe signal generating member will cease. The plunger rod and the signalgenerating member are thus designed such that the axial overlap of thefirst section and signal generating member in the initial position ofthe plunger rod corresponds to, i.e. is equal to or essentially equalto, said distance. Hence, the first section only supports the signalgenerating member during axial displacement of the plunger rod distancecorresponding to a distance necessary for commencement of medicamentexpulsion. When the plunger rod has been displaced by an amountcorresponding to this distance, the signal generating member will beallowed to flex radially inwards towards its radially unbiased state.The signal generating member will thereby disengage from the tubularextension member. The signal generating member, which is biased in thedistal direction by the first energy accumulation member will thereby nolonger be retained by the tubular extension member and will therefore bethrown towards the distal inner surface of the tubular extension member.This results in an audible “click” sound, and also provides the userwith a tactile sensation.

The medicament delivery device may furthermore comprise a medicamentdelivery member cover received by and rotationally interlocked with thehousing, and a tubular rotator arranged to receive the plunger rod andthe tubular extension member. The medicament delivery member cover isdisplaceable axially, between an extended position and a retractedrelative to the housing. The medicament delivery member cover is biasedtowards the extended position.

The tubular rotator is arranged to interact with the medicament deliverymember, and has a guide structure arranged to convert linear motion ofthe medicament delivery member to rotational motion of the tubularrotator.

FIG. 1 shows an example of a medicament delivery device. The medicamentdelivery device 1 comprises a housing 3, having a proximal end 3 a and adistal end 3 b, a tubular extension member 5, for example a rear capmember, mounted at the distal end of the housing 3, and a medicamentdelivery member cover 7, e.g. a needle cover, arranged to be received bythe housing 3 and arranged to be biased in the proximal direction.

FIG. 2 depicts an exploded view of the medicament delivery device 1. Themedicament delivery device 1 further comprises a plunger rod 11 which isarranged to be biased towards the proximal end 3 a, a plunger 13, afirst resilient member, i.e. an energy accumulation member, 15 arrangedto bias the plunger rod 11 in the proximal direction, which first energyaccumulation member 15 may be a spring for example, a second resilientmember or energy accumulation member 9, arranged to bias the medicamentdelivery member cover 7 in the proximal direction, a tubular rotator 17arranged to receive the plunger rod 11 and the first energy accumulationmember 15, tubular extension member 5 which is axially and rotationallyfixed relative to the housing 3, a tubular operation member 17, in thefollowing referred to as tubular rotator 17, arranged to receive aportion of the rear end cap 7 and the plunger rod 11, a rod 19 which thefirst energy accumulation member 15 is arranged to receive, and a signalgenerating member 21, which in the following will be exemplified by aU-shaped bracket, hereinafter referred to as “U-bracket”. Theexemplified medicament delivery device 1 furthermore comprises amedicament container holder 23 and a medicament container 25 providedwith a needle 25 a. The plunger 13 is arranged to run in the medicamentcontainer 25 by linear displacement of the plunger rod 11, to therebyexpel medicament through the needle 25 a.

The plunger rod 11, the tubular extension member 5, the tubularoperation member 17, the energy accumulation member 15 and the signalgenerating member 21 form an automatic feedback mechanism 12, or simplya feedback mechanism, for the medicament delivery device 1. The feedbackmechanism 10 is arranged to notify a user of a start of expulsion ofmedicament from the medicament container 25.

According to the present example, the plunger rod 11 has a radialopening 11 a, and the tubular extension member 5 which is arranged toreceive the plunger rod 11 has a corresponding flexible tongue 5 aflexible in the radial direction and arranged to engage with the opening11 a. The tubular rotator 17 is arranged to receive a portion of thetubular extension member 5, in particular that portion which comprisesthe flexible tongue 5 a.

The tubular rotator 17 is rotatable from an initial rotational positionto a final rotational position. In its initial rotational position thetubular rotator 17 is arranged to push the flexible tongue 5 a intoengagement with the opening 11 a, preventing the plunger rod 11 fromaxial displacement. When the tubular rotator 17 is rotated, the innerstructure of the tubular rotator 17 is designed such that it willprovide less radial force on the flexible tongue 5 a, allowing theflexible tongue 5 a to flex radially outwards to disengage from theplunger rod 11. The plunger rod 11, which is biased in the proximaldirection, is thereby displaced axially and medicament administration isthus commenced as the plunger rod 15 pushes the plunger 13 inside themedicament container 25.

As shown in FIG. 3 a , the tubular rotator 17 has a centralthrough-opening 17 a extending from the proximal end to the distal endof the tubular rotator 17. The tubular rotator 17 is arranged to receivethe tubular extension member 5 and the plunger rod 11 in thethrough-opening 17 a.

The tubular rotator 17 furthermore comprises a guide structure 17 b. Theguide structure 17 b is arranged to interact with the medicamentdelivery member cover 7, in particular to convert linear motion of themedicament delivery member cover 7 to rotational motion of the tubularrotator 17.

FIG. 4 a shows a first example of a plunger rod 11, and U-bracket 21.The U-bracket 21 has a distal transversal end portion 21 a and two legs21 b connected by the distal transversal end portion 21 a. Moreover, theU-bracket 21 has two radial feet 21 c. Each radial foot 21 c extendsfrom a respective leg 21 b.

The plunger rod 11 has a hollow body 11 b and a distal end opening 11 c.The plunger rod 11 is arranged to receive the first energy accumulationmember 15 in the distal end opening 11 c, such that the first energyaccumulation member 15 extends in the distal direction out from thedistal end opening 11 d. The plunger rod 11 is arranged to retain theproximal end of the first energy accumulation member 15 in the hollowbody 11 b to enable biasing by means of the first energy accumulationmember 15. The U-bracket 21 is arranged to receive the plunger rod 11,from the distal end of the plunger rod 11, and the first energyaccumulation member 15 is arranged to be compressed between the distaltransverse end portion 21 a and a stop inside the plunger rod 11 whenthe plunger rod 11 is in the initial position. In the initial positionof the plunger rod 11, the radial feet 21 c are in engagement with therear end cap 5.

The exemplified plunger rod 11 has an external surface that has a firstsection 12 a provided with a first guide structure 11 d arranged tosupport the U-bracket 21 and flex the U-bracket 21 radially outwards toenable the radial feet 21 c to engage with the tubular extension member5. The first section 12 a, and in particular the first guide structure11 d, has a dimension in the transverse direction perpendicular to thelongitudinal direction of the plunger rod 11, which is greater than thedistance between the two radial feet 21 c in a radially unbiased stateof the U-bracket 21. The first guide structure 11 d hence pushes theU-bracket 21 radially outwards when the U-bracket bears against thefirst guide structure 11 d. The first guide structure 11 d includesaxial grooves, of which only one is shown in FIG. 4 a ; the other onebeing at 180 degrees relative to the illustrated axial groove. The firstguide structure 11 d facilitates guiding relative linear movementbetween the plunger rod 11 and the U-bracket. In particular, the legs 21b are arranged to slide in the axial grooves 11 d.

In the initial position of the plunger rod 11 the axial overlap of thefirst section 12 a, in particular the first guide structure 11 d, andthe U-bracket 21 corresponds to the distance of axial displacement ofthe plunger rod 11 necessary for commencement of medicament expulsion.This distance corresponds to the distance from the proximal end of theplunger rod 11 to the distal end of the plunger 13, in the initialposition of the plunger rod 11. The initial overlap may be a littlelonger or a little shorter than the distance from the proximal end ofthe plunger rod to the distal end of the plunger. This applies to anyvariation disclosed herein.

The plunger rod 11 has a second section 12 b arranged distally from andcontiguous to the first section 12 a. According to the present example,the second section 12 b is defined by a longitudinal axially extendingradial opening 11 e allowing radial inwards flexing of the U-bracket 21towards its radially unbiased state. To this end, in the second section12 b the channel forming the distal end opening 11 c is open to thesides, i.e. in the radial direction. The longitudinal axially extendingradial opening 11 e has a longitudinal extension aligned with the firstguide structure 11 d. The transverse dimension of the plunger rod 11 ishere due to the longitudinal axially extending radial opening 11 dsmaller than it is in the first section 12 a. The U-bracket 21 isallowed to flex radially inwards towards its radially unbiased state,only limited by the diameter of the first energy accumulation member 15.This radial inwards flexing of the U-bracket 21 is sufficient todisengage the radial feet 21 c from the rear end cap 5.

The exemplified plunger rod 11 furthermore has a third section 12 carranged distally from and contiguous to the second section 12 b. Thethird section 12 c is defined by a second guide structure 11 f arrangedto guide the U-bracket 21 axially. The second guide structure 11 f isaxially aligned with the longitudinal extending radial opening 11 e. Thesecond guide structure 11 f may for example comprise two axial grooves,of which one is shown in FIG. 4 a . The second guide structure 11 f hasa greater transverse dimension than the longitudinal axially extendingradial opening 11 d. To this end, the third section 12 c is arranged tosupport and flex the U-bracket 21 radially outwards allowing theU-bracket to again engage with the tubular extension member 5.

FIG. 4 b shows the plunger rod 11 and the U-bracket 21 in a mountedstate, i.e. when the U-bracket 21 has received the plunger rod 11. Thisis in particular their relative position in the initial position of theplunge rod 11. It may be seen that the first energy accumulation member15 is in a compressed state in which it biases the plunger rod 11 in theproximal direction and the U-bracket 21 in the distal direction. Itshould here be noted that this compressed state is obtained when theplunger rod 11 is prevented from axial displacement by engagement withthe flexible tongue 5 a of the tubular extension member 5 and theU-bracket 21 is in engagement with the tubular extension member 5.

With reference to FIGS. 5 a-c the operation of the plunger rod 11 andthe U-bracket 21 will now be described in more detail. In FIG. 5 a themedicament delivery device 1 is in a state ready for use. The plungerrod 11 is in the initial position. The U-bracket 21 is in a firstposition in which it bears against the first section 12 a, in particularthe first guide structure 11 d. The U-bracket 21 is hence flexedradially and in engagement with the tubular extension member 5. Thetubular extension member 5 has first engagement means 5 c for engagementwith the U-bracket 21. The first engagement means 5 c may for example bea proximal end edge of the tubular extension member 5 or radial recess,with which the radial feet 21 c may engage. The first energyaccumulation member 15 is hence in a compressed state, biasing theplunger rod 11 and the U-bracket 21 in opposite directions. The tubularextension member 5 has a distal inner surface 5 b defining a distal endof the central opening of the tubular extension member 5 in which theplunger rod 11 and the U-bracket 21 are arranged. The U-bracket 21 isdistanced by distance D from the distal inner surface 5 b.

The plunger rod 11 and the plunger 13 are in contact with each other inthe initial position of the plunger rod 11. There is however a play, ordistance d, between the plunger rod 11 and the distal end of the plunger13. The plunger rod 11 has to be displaced the distance d before it candisplace the plunger 13 axially. This distance d corresponds to thedistance that the plunger rod 11 must travel in order for medicamentexpulsion to commence. This is also the size of the axial overlap of thefirst section 12 a and the U-bracket 21 in the initial position of theplunger rod 11.

In FIG. 5 b , the medicament delivery device 1 is shown duringmedicament expulsion. Here, the plunger rod 11 has been released fromengagement with the tubular extension member 5 due to the rotation ofthe tubular rotator 17. In the illustration in FIG. 5 b , the plungerrod 11 has been displaced in the proximal direction and it has bridgedthe initial gap, or distance d, to the plunger 13. Medicament expulsionhas hence commenced. The U-bracket 21 has moreover been released fromits initial engagement with the rear end cap 5, as the displacement ofthe plunger rod 11 has resulted in that the second section 12 b of theplunger rod 11 has reached the proximal end of the U-bracket 21, wherebythe U-bracket 21 has been able to flex radially inwards towards itsradially unbiased position. The U-bracket 21 has thus been rapidlydisplaced in the distal direction until reaching the distal innersurface 5 b of the tubular extension member 5. The opposite directionalmotion of the plunger rod 11 and the U-bracket 21 is generally shown bythe two arrows. This collision results in an audible “click”, and invibration of the medicament delivery device 1. The user hence becomesaware of that medicament expulsion has commenced. The user may then, forexample, count 10-15 seconds before removing the medicament deliverydevice 1 from the injection site.

The U-bracket 21 may in its end position in which it has collided withthe distal inner surface 5 b, engage with the tubular extension member5. The tubular extension member 5 may therefore have radial openings 5 darranged distally from and aligned with the first engagement means 5 c.In particular, the radial feet 21 c may be received in the radialopenings 5 d to enable the plunger rod 11 to move past the U-bracket 21during medicament expulsion, in particular as the third section 12 cpasses by the proximal end of the U-bracket 21. FIG. 5 c shows themedicament delivery device 1 in a final state, after medicament deliveryhas been finalised and the plunger rod 11 has moved past the U-bracket21 in the proximal direction.

FIG. 6 shows a second example of a tubular extension member 5 and aplunger rod 11-1. FIG. 7 a shows the plunger rod 11-1 in more detail.Plunger rod 11-1 is similar to the previously described plunger rod 11.Plunger rod 11-1 also has a first section 12 a like plunger rod 11, i.e.with a first guide structure 11 d. Plunger rod 11-1 however has a secondsection 12 b arranged distally from and contiguous to the first section12 a, which second section extends to the distal end 14 of the plungerrod 11-1. The second section 12 b is also in this example defined by alongitudinal axially extending radial opening 11 e allowing radialinwards flexing of the U-bracket 21 towards its radially unbiased state.To this end, in the second section 12 b may be formed by two axialcut-outs extending from the distal end 14 of the plunger rod 11-1 tofirst section 12 a, splitting the distal portion of the plunger rod11-1. The longitudinal axially extending radial opening 11 e has alongitudinal extension aligned with the first guide structure 11 d. Thetransverse dimension of the plunger rod 11 is due to the longitudinalaxially extending radial opening 11 d smaller than it is in the firstsection 12 a. The U-bracket 21 is here allowed to flex radially inwardstowards its radially unbiased state, only limited by the diameter of thefirst energy accumulation member 15. This radial inwards flexing of theU-bracket 21 is sufficient to disengage the radial feet 21 c from therear end cap 5.

The operation of this variation of the medicament delivery device 1 issimilar to that described above with reference to FIGS. 5 a -c. Thetubular extension member 5 does however not have radial openingsarranged distally from the first engagement means in order to enable theplunger rod 11-1 to pass the U-bracket 21. Since the open second section12 b of plunger rod 11-1 extends until the distal end 14, the U-bracket21 can be accommodated in the longitudinal axially extending radialopening the entire way as the plunger rod 11-1 moves past the U-bracket21. FIG. 7 b shows the plunger rod 11-1 and the U-bracket 21 in anassembled state.

With reference to FIG. 8 another example of a plunger rod and U-bracketis shown. According to this variation, the U-bracket 21-1 is shorterrelative to the plunger rod 11-2 than the U-bracket 21 is relative tothe plunger rods 11 and 11-1. Plunger rod 11-2 is adapted to the designof U-bracket 21-1. To this end, plunger rod 11-2 has an external surfacethat has a first section 12 a provided with a first guide structure 11 darranged to support the U-bracket 21-1 and flex the U-bracket 21-1radially outwards to enable the radial feet 21 c to engage with thetubular extension member 5. The first section 12 a, and in particularthe first guide structure 11 d, has a dimension in the transversedirection perpendicular to the longitudinal direction of the plunger rod11-2, is greater than the distance between the radial feet 21 c in theradially unbiased state of the U-bracket 21-1. The first guide structure11 d hence pushes the U-bracket 21-1 radially outwards when theU-bracket bears against the first section 12 a.

The first guide structure 11 d includes axial grooves, of which only oneis shown in FIG. 8 . The first guide structure 11 d facilitates guidingrelative linear movement between the plunger rod 11-2 and the U-bracket21-1.

The first section 12 a extends the entire way to the distal end 14 ofthe plunger rod 11-2. In the initial position of the plunger rod 11-2the axial overlap between the first section 12 a and the U-bracket 21-1corresponds to the distance of axial displacement of the plunger rod11-2 necessary for commencement of medicament expulsion

FIGS. 9 a-9 b show the operation of a medicament delivery device 1including the plunger rod 11-2 and the U-bracket 21-1. The tubularextension member 5-1 has first engagement means 5 c, which in thepresent case are exemplified by radial openings. As shown in FIG. 9 athe radial feet 21 c of the U-bracket 21-1 are initially, i.e. in theinitial position of the plunger rod 11-2, in engagement with the radialopenings. When the plunger rod 11-2 is released by rotation of thetubular rotator 17, the plunger rod 11-2 is displaced in the proximaldirection bridging the gap d between the distal end of the plunger 13and the proximal end of the plunger rod 11-2. The plunger rod 11-2 willthus generally have been displaced enough to slide out beneath theU-bracket 21-1 to thereby allow the U-bracket 21 to flex radiallyinwards towards its radially unbiased state. The U-bracket 21 is hencedisengaged from the tubular extension member 5-1 and is thereby due toits biased state rapidly displaced in the distal direction, subsequentlycolliding with the distal inner surface 5 b of the tubular extensionmember 5-1. Again, audible “click” is thereby generated, and vibrationsare induced in the medicament delivery device 1. FIG. 9 b shows when theU-bracket 21 has collided with the distal inner surface 5 b.

Any variation disclosed herein may be utilised with an electromechanicalsensor and a recording unit provided with electronic components, andwhich recording unit may be attachable to and detachable from thehousing. The electromechanical sensor may be arranged to detect when theU-bracket collides with the distal inner surface. According to thisvariation the medicament delivery device includes an injection endmember which is axially displaceable and arranged to interact with theU-bracket. The tubular extension member has a distal through-opening inwhich the injection end member is movably arranged. When medicamentexpulsion commences, the U-bracket is released and due to the biasingprovided by the first energy accumulation member, is pushed in thedistal direction. As a result the injection end member which is axiallyaligned and located distally relative to the U-bracket, is pushedaxially in the distal direction by the U-bracket, as allowed by its freelocation in the distal through-opening. The injection end member willthereby actuate the electromechanical sensor arranged to detectdisplacement of the injection end member when medicament expulsion iscommenced. In this manner detection of commencement of medicamentexpulsion may be presented to the user by the recording unit or by anexternal device in communication with the recording unit.

The inventive concept has mainly been described above with reference toa few examples. However, as is readily appreciated by a person skilledin the art, other embodiments than the ones disclosed above are equallypossible within the scope of the inventive concept, as defined by theappended claims.

The invention claimed is:
 1. A medicament delivery device that notifiesa user of a start of expulsion of medicament from a medicamentcontainer, wherein the medicament delivery device comprises: a housing;a needle cover slidably positioned within the housing and having a firstaxial position and a second axial position; a signal generating membercomprising two proximally extending legs; a plunger rod releasably fixedrelative to the housing in a pre-tensioned state, where the plunger rodis hollow and has an open distal end and a proximal end; and a springpositioned within the plunger rod, where the spring is compressed whenthe plunger rod is in the pre-tensioned state biasing the proximal endto move the plunger rod proximally and biasing the signal generatingmember to axially move in a distal direction, wherein the signalgenerating member is arranged to partially surround the plunger rod,wherein axial movement of the needle cover from the first axial positionto the second axial position releases the plunger rod causingdecompression of the spring so that the spring simultaneously drives thesignal generating member distally relative to the housing to generate anaudible signal indicating that medicament expulsion from the medicamentcontainer has just commenced.
 2. The medicament delivery device of claim1, wherein the signal generating member is U-Shaped and has a distaltransversal end portion.
 3. The medicament delivery device of claim 1,wherein each leg comprises a foot at a terminal proximal end.
 4. Themedicament delivery device of claim 1, wherein the legs flex radiallyprior to the generation of the audible signal.
 5. The medicamentdelivery device of claim 1 further comprises a rod that is positionedwithin the spring, where the rod has a longitudinal axis.
 6. Themedicament delivery device of claim 5, wherein the signal generatingmember flexes radially relative to the longitudinal axis when the needlecover moves from the first axial position to the second axial position.7. The medicament delivery device as claimed in claim 1 wherein thesignal generating member comprises an elongated U-shaped bracketsupporting the two proximally extending legs, where each leg is flexibleand is provided with radial feet extending radially relative to alongitudinal axis of the housing.
 8. The medicament delivery device asclaimed in claim 1, wherein the plunger rod has an external surfaceconfigured to operatively engage the legs of the signal generatingmember radially outwards, and to guide axial displacement of the signalgenerating member.